Method of controlling the differential dissolution rate of photoresist compositions, polycyclic olefin polymers and monomers used for making such polymers

ABSTRACT

A photoresist composition encompassing a polymer having at least one polycyclic olefin repeat unit having a desired exo mole percent is provided, where the repeat unit is derived from a polycyclic olefin monomer having the desired exo mole percent. Such polymers having such repeat units having a desired exo mole percent offer control of differential dissolution rate and hence provide enhanced imaging properties. Exemplary monomers having a desired exo mole percent are also provided

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 60/449,785 filed on Feb.24, 2003.

TECHNICAL FIELD

[0002] The present invention relates generally to controlling thedissolution rate of polymers used in forming photoresist compositionsand more specifically to polymers having a cycloalkyl repeat unit forcontrolling the dissolution rate of such polymers in photoresistcompositions and the compositions thereof.

BACKGROUND

[0003] Photoresists are photosensitive films used for transferring animage formed therein to an underlying layer or substrate. A layer of aphotoresist is formed over a substrate and generally a layer of amaterial to which the image is to be transferred. The photoresist layeris then exposed through a photomask to a source of activating radiationwhere the photomask has some areas that are opaque to such radiation andother areas that are transparent. A photoinduced chemical transformationresults in the areas exposed to the activating radiation which allowsfor the development of a relief image therein.

[0004] Photoresists can be either positive-tone or negative-tone.Generally, negative-tone photoresists undergo a crosslinking reactionwithin those portions of the photoresist layer that are exposed toactivating radiation. As a result, the exposed portions become lesssoluble than unexposed portions in a solution used to develop the reliefimage. In contrast, for positive-tone photoresists, the exposed portionsof the photoresist layer become more soluble, in a developer solution,than the portions unexposed to such radiation.

[0005] As microelectronic devices, such as integrated circuits, employsmaller and smaller device structures to effect their function, the needfor photoresist compositions capable of resolving such device structuresbecomes increasingly important. While the ability of a particularphotoresist composition to resolve a particular device structure is afunction of many factors, one such factor is control of the differencein the dissolution rates of exposed and unexposed portions of thephotoresist. While this factor has been studied previously, the thrustof such study has generally been to develop additives that might serveto increase the difference in the dissolution rate of such exposed andunexposed portions in a developer solution. However, such additives canaffect other properties of the photoresist composition in a less thandesirable manner, for example by increasing the optical density of thecomposition at the working wavelength of the activating radiation, andperhaps of more import, merely increasing the difference in thedissolution rates of exposed and unexposed regions does not alwayscontrol the differential dissolution rate.

[0006] Thus it would be desirable to provide photoresist compositionswith controlled differential dissolutions rates. That is to say, thedifference between the dissolution rates of exposed and unexposedportions of the photoresist is controllable. It would also be desirablefor such photoresist compositions to encompass a polymeric material thatprovides such control of the differential dissolution rate without theneed for an additive. In addition, it would be desirable to provide suchpolymeric materials for use as base resins of such photoresistcompositions and to provide methods of forming such desirable polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a pictorial representation of an exo and an endo isomerof 5-methyl-2-norbornene;

[0008]FIG. 2 is a table showing the exo/endo isomer ratio of the severalα,α-bis(trifluoromethyl)bicyclo[2.2.1]hept-5-ene-2-ethanol (HFANB)monomers used for polymerizations in accordance with embodiments of thepresent invention;

[0009]FIG. 3 is a three dimensional bar graph that plots dissolutionrate versus molecular weight and exo isomer mole percent for exemplaryembodiments in accordance with the present invention;

[0010]FIG. 4 presents scanning electron micrographs of polymer blendshaving about 50 wt % of a homopolymer having selected exo mol % and arelatively high molecular weight; and

[0011]FIG. 5 presents scanning electron micrographs of polymer blendshaving about 50 wt % of a homopolymer having selected exo mol % and arelatively low molecular weight.

DETAILED DESCRIPTION

[0012] The preparation of norbornene derivatives, hereinafter referredto as monomers that are useful for forming polycyclic olefin resins,generally results in a mixture of exo and endo isomers being formed (seeFIG. 1). Generally, purification of a reaction mixture from thesynthesis of a monomer useful in embodiments of the present inventionencompasses fractional distillation methods. It has been observed thatdifferent fractions collected from such a distillation have differentratios of the aforementioned exo and endo isomers (see, FIG. 2). Todetermine what effect such differences in the isomer ratio might have onthe characteristics of polymers formed from the different fractions,homopolymers were formed of each of the several fractions.

[0013] Advantageously, it has been found that the resultant polycyclicolefin resins exhibited unexpected variations in their dissolution rate.Unexpected because rather than observing the dissolution rate of suchresins varying as a function of molecular weight (either expressed as Mnor Mw) as normally observed, the variations seem to be primarily afunction of the ratio of exo to endo isomers in the monomer startingmaterial (see, FIG. 3).

[0014] For example a first resin with Mn=3560 polymerized from a monomerhaving an exo isomer mole percent (mol %) of 48, is found to have adissolution rate (DR) of 3920 Angstroms per sec (Å/sec) while a second,analogous resin polymerized from the same starting monomer but withapproximately twice the molecular weight (Mn=7520) is found to have a DRof 3850 Å/sec. Thus, unexpectedly, resins having very differentmolecular weights have essentially the same DR (see, Examples 21 and 22in Table 1). Similarly, for a third resin with Mn=3270 and polymerizedfrom a monomer having 22 mol % of the exo isomer, the DR is found to be6627 Å/sec, while an analogous fourth resin with Mn=13700 againpolymerized from the same starting monomer but having about four timesthe molecular weight is found to have essentially the same DR (DR=6543Å/sec., see, Examples 16 and 20 in Table 1).

[0015] For each of the above examples, the resin is a homopolymer of,α,α-bis(trifluoromethyl)bicyclo[2.2.1]hept-5-ene-2-ethanol (HFANB),formed in essentially the same manner. Thus, for each of the pairs (21and 22, 16 and 20), only the concentration of a chain transfer agentused for the polymerization is changed to provide polymers havingdifferent molecular weights.

[0016] Comparing the DR of the first pair of resins (21 and 22) to thesecond pair of resins (16 and 20), it is apparent that the second pairof resins has a DR of about twice that of the first pair of resins. Asboth pairs of resins are HFANB homopolymers differing only in the molepercent of exo isomer in the starting monomer, Applicants believe thatthis difference in dissolution rate is a function of this difference inexo isomer mole percent. Thus it seems that where the concentration ofexo isomer in the starting monomer is decreased, for example from 48 mol% in the first pair of resins to 22 mol % in the second pair of resins,the dissolution rate is increased.

[0017] Turning to FIG. 3, a three dimensional bar graph showing valuesof DR versus exo mol % versus molecular weight (Mn) for each of Examples12-23 (see, Table 1), illustrates this relationship. However, it will benoted that rather than a linear relationship between exo mol % and DR,there appears to be a threshold at a value of exo mol % between about25% and 40%. That is to say, a first range of exo isomer contents seemsto exhibit a relatively constant first DR (between about 6000 to 7200Å/sec), while a second range of exo isomer contents seems to exhibit arelatively constant second DR (between about 3500 and 4000 Å/sec)significantly different from the first DR.

[0018] It should be noted that while the Applicants advance no specifictheory to explain the unexpected results observed (see above and FIG.3), it is well known that the dissolution rate of a polymer is afunction of its solubility in developer solutions, which is in turn afunction of the specific pendant group substituents present on therepeat units that form the polymer backbone. In addition, where thoserepeat units are derived from polycyclic olefins, polymer solubilitywill also be a function of whether pendant groups are substituted in anexo or endo position as it is well known that the reactivity of apendant group is higher where that group is exo substituted as opposedto the same group being endo substituted. Therefore, while it has beengenerally observed that polymer dissolution rate is often a function ofmolecular weight, where other factors are the same, Applicants believethat the dissolution rate of a polymer can be effectively controlled byaltering whether a reactive pendant group's substitution into an exoposition of a polymer repeat unit is enhanced or diminished with whatnormally is expected.

[0019] Not withstanding the above, it is also well known thatunderstanding the dissolution rate behavior of binder resins, is bothimportant in the development of high performance photoresistformulations and complex. For example, Ito, et al., Proceedings of SPIE,2003, 5039, 70 reported that homopolymers of HFANB made with both Ni andPd catalysts exhibited “no straightforward relationship betweendissolution rate [in 0.26 N TMAH] and Mn or Mw” when investigated usingquartz crystal microbalance methods. Ito also investigated thedissolution rate behavior of the same polymers using a more dilute, 0.21N, TMAH solution but found the dissolution behavior complex andseemingly dependant on the molecular weight polydispersity of thepolymer. Hoskins et al, Proceedings of SPIE, 2003, 5039, 600, reportedthe dissolution rate behavior of HFANB homopolymers in a 0.19 N TMAHsolution where the homopolymers were made using only Pd catalysts. Usingoptical interferometric methods to measure dissolution rates, Hoskinsreported that the HFANB homopolymers were found to “exhibit an a typicaldependence of dissolution rate on molecular weight”. Thus Hoskins foundthat low molecular weight HFANB homopolymers (Mw<10,000) exhibiteddecreasing dissolution rates with increasing molecular weights whilehomopolymers with Mw>10,000 but <100,000 exhibited increasingdissolution rates with increasing molecular weight. However, it shouldbe noted that the molecular weight polydispersity of the Hoskins sampleswere quite broad, ranging from 1.91 to 9.21, thus potentiallycomplicating interpretation of the dissolution rate behavior.

[0020] Therefore, to simplify the investigation of dissolution ratebehavior, Applicants elected to prepare HFANB homopolymers using only Pdcatalysts and process conditions that would result in relatively narrowmolecular weight polydispersities (i.e., 1.50 to 2.50). In addition, andto further avoid complexities, Applicants measured the dissolution ratebehavior of such homopolymers using only a standard 0.26 N TMAH solutionand quartz crystal microbalance methods.

[0021] Thus, by and through obtaining this increased understanding ofdissolution rate behavior, Applicants believe that it is possible tocreate binder resins for photoresist compositions, both positive-actingand negative-acting, that take advantage of this understanding and henceallow for the difference between the dissolution rate of exposed andunexposed portions of photoresist layers (the differential dissolutionrate) to be controlled. Additionally, it is believed and shown hereinthat this understanding can lead to better imaging results over abroader range of polymer parameters, for example variations in molecularweight. It should be further noted that the selection of HFANB monomersfor the homopolymers studied, was also influenced by the use of suchmonomers in a large number of photoresist binder resin formulations thathave been reported and thus the understanding obtained would be morereadily applied.

[0022] In addition, the homopolymers used in the dissolution rate studywere prepared using both olefinic and non-olefinic chain transfer agents(CTAs). Analysis of the homopolymers so formed, indicates that physicalcharacteristics of the polymers, for example Mw, Mn, OD (opticaldensity) and the like, can be varied by the choice of the CTA employedduring the polymerization:

[0023] While the above observations were of homopolymers formed by vinyladdition polymerization, it has been shown that polymers formed usingmore than one type of monomer will exhibit similar dissolution rateeffects that should also lead to enhanced imaging. Therefore, themonomers that will be useful in the practice of embodiments inaccordance with the present invention are described below where thepolymers formed from such monomers will encompass at least one monomerhaving a desired exo isomer mol %.

[0024] Embodiments in accordance with the present invention includerepeat units derived from norbornene-type monomers having an acid labileprotected pendant group. Such monomers are represented by Formula A,below:

[0025] where m and Z are defined above and where at least one of R¹, R²,R³, or R⁴, independently, is an acid labile protected pendant group thatis cleavable by, for example, an acid generated from a photoacidgenerator. Any known acid labile group known to the literature and tothe art can be utilized in the present invention such as those set forthherein with regard to Formula A.

[0026] The remaining one or more R1, R2, R3, or R4, groups,independently, can be hydrogen, or a hydrocarbyl having from 1 to about20 carbon atoms, or halogens selected from F, Cl or Br, or a hydrocarbylhaving from 1 to about 20 carbon atoms substituted at any hydrogen atomwith an O, S, N, or Si, and the like, or a fluorinated hydrocarbylhaving from 1 to about 20 carbon atoms wherein each carbon atom,independently; is substituted with 0, 1, 2, or 3 fluorine atoms.

[0027] Returning to descriptions of acid labile protected groups, insome embodiments, such groups are a fluorinated carbinol moiety havingfrom 1 to about 20 carbon atoms wherein each carbon atom, independently,is substituted with 0, 1, 2, or 3 fluorine atoms and the oxygen atom isprotected by an acid labile group (i.e., blocking or protective groups)that are cleavable by acids generated from a photoacid generator.Exemplary fluorinated groups include, among others, —(CR₂)_(n)OR′,—(O—(CH₂)_(n))_(n)—C(CF₃)₂—OR′, —(CH₂O)_(n)—C(CF₃)₂—OR′,—((CH₂)_(n)O)_(n)—CH₂—C(OR′)(CF₃)₂ where each occurrence of n is anindependently selected integer from 0 to about 5, each occurrence of Ris independently a hydrogen or a halogen (i.e., F, Cl, Br, I) and whereR′ is the acid labile group. R′ includes, but is not limited to,—CH₂OCH₃ (dimethyl ether), —CH₂OCH₂CH₃ (methyl ethyl ether), —C(CH₃)₃,—Si(CH₃)₃, —CH₂Q(O)O(t-Bu), 2-methylnorbornyl, 2-methylisobornyl,2-methyl-2-adamantyl, tetrahydrofuranyl, tetrahydropyranoyl,3-oxocyclohexanonyl, mevalonic lactonyl, dicyclopropylmethyl (Dcpm), ordimethylcyclopropylmethyl (Dmcp) groups, or R′ is —C(O)OR″ where R″ is—C(CH₃)₃, —Si(CH₃)₃, 2-methylnorbornyl, 2-methylisobornyl,2-methyl-2-adamantyl, tetrahydrofuranyl, tetrahydropyranoyl,3-oxocyclohexanonyl, mevalonic lactonyl, Dcpm, or Dmcp groups, orcombinations thereof.

[0028] In some embodiments of the present invention, Formula A is alsorepresented by Formula A1, below

[0029] where n and R′ are as previously defined. More specifically,exemplary monomers encompassing an acid labile protected pendant groupin accordance with Formula A1 encompass:

[0030] Additionally, norbornene-type monomers in accordance with FormulaA are represented by Formula A2, below:

[0031] where n′ is an integer from 0 to 5 and R^(a), R^(b), and R^(c),independently, represent linear or branched hydrocarbyl groups from C₁to about C₂₀ or R^(a) and R^(b) taken together along with the commoncarbon to which they are attached represent a saturated cyclic groupcontaining 4 to 12 carbon atoms. An exemplary norbornene-type monomer inaccordance with Formula A2 encompasses:

[0032] where tBu is a tertiary butyl group.

[0033] Some embodiments of the present invention include repeat unitsderived from norbornene-type monomers having a crosslinking capablependant group. Such monomers are represented by Formula B, below:

[0034] where m and Z are defined as above, and where each of R⁵, R⁶, R⁷and R⁸, independently, are H, a halogen, a linear, branched or cyclic C₁to C₃₀ alkyl, an alkylol, an aryl, an aralkyl, an alkaryl, an alkenyl oran alkynyl; with the proviso that at least one of R⁵, R⁶, R⁷ and R⁸ is afunctional group that is capable of crosslinking. Suitable crosslinkingcapable functional groups include, but are not limited to, hydroxy alkylethers according to Formula I:

-A-O—[—(CR″₂)_(q)—O—]_(p)—(CR″₂)_(q)—OH  Formula I

[0035] where A is a linking group selected from C₁ to C₆ linear,branched, or cyclic alkylene, each occurrence of R** is independentlyselected from H, methyl and ethyl, q is independently an integer from 1to 5, in some cases from 2 to 5, and p is an integer from 0 to 3.

[0036] Other suitable crosslinking capable functional groups arerepresented by Formulae II, III, IV and V:

—R′″-Q  Formula II

—(CH₂)_(n)C(O)OR^(#)  Formula III

—(CH₂)_(t)—C(CF₃)₂—O—(CH₂)_(t)—CO—(OR^(##))  Formula IV

[0037] where for Formula II, R′″ is a linear, branched or cyclic C₁ toC₃₀ alkylene, arylene, aralkylene, alkarylene, alkenylene or alkynylenelinking group that is optionally partially or completely halogenated,and Q is a functional group selected from hydroxyl, carboxylic acid,amine, thiol, isocyanate and epoxy. For Formula III, n is as previouslydefined and R^(#) represents an acid labile group cleavable by aphotoacid generator. Finally for Formula IV, each occurrence of t isindependently an integer from 1 to 6 and R## is a C₁-C₈ linear orbranched alkyl moiety, and in some instances a t-butyl group.

[0038] In addition, some embodiments in accordance with the presentinvention include repeat units derived from norbornene-type monomershaving pendant groups that are exclusive of acid labile protected groupsand crosslinking capable groups. Such monomers are represented byFormula C, below:

[0039] where m and Z are as previously defined, and where substitutentsR⁹, R¹⁰, R¹¹ and R¹², are each an independently selected neutralsubstituent selected from the group of substituents consisting ofhalogens (i.e., F, Cl, or Br), —(CH₂)_(n)—C(O)OR²¹,—(CH₂)_(n)—(CM₂)_(n)—OR¹⁸, —(CM₂)_(n)—OC(O)R∫, —(CH₂)_(n)—OC(O)OR¹⁷,—(CH₂)_(n)—C(O)R¹⁸, —(CH₂)_(n)C(R¹⁹)₂CH(R¹⁹)(C(O)OR²⁰),—(CH₂)_(n)—NH—(SO₂)—CF₃, —(CH₂)_(n)C(R¹⁹)₂CH(C(O)OR²⁰)₂, —C(O)O—(CH₂,—OR¹⁸ and —(CH₂)_(n)—O—(CH₂)_(n)—OR¹⁸,—(CH₂)_(n)—(O—(CH₂)_(n))_(n)—C(CF₃)₂OR²¹ where each occurrence of n isindependently an integer from 0 to 5, M can be hydrogen or a halogen(i.e., F, Cl, or Br), R¹⁹ can independently be hydrogen, a halogen, alinear or branched C₁ to C₁₀ alkyl group or cycloalkyl group or a linearor branched C₁ to C₁₀ halogenated alkyl group or halogenated cycloalkylgroup, R¹⁸ can independently be hydrogen, a linear or branched C₁ to C₁₀alkyl group or cycloalkyl group or a linear or branched C₁ to C₁₀halogenated alkyl group or halogenated cycloalkyl group, R²⁰ is notreadily cleavable by a photoacid generator and can independently be alinear or branched C₁ to C₁₀ alkyl group or cycloalkyl group or a linearor branched C¹ to C₁₀ halogenated alkyl group or halogenated cycloalkylgroup, R¹⁷ is not readily cleavable by a photoacid generator and canindependently be linear or branched C₁ to C₁₀ alkyls or halogenatedalkyls, a monocyclic or poIycyclic C₄ to C₂₀ cycloaliphatic orhalogenated cycloalkyl moiety, a cyclic ether, a cyclic ketone or acyclic ester (lactone), where each of the cyclic ether, ketone and estercan be halogenated or not and R²¹ is defined as R¹⁷ plus hydrogen.Exemplary cycloaliphatic moieties include, but are not limited to,unsubstituted cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl groups aswell as 1-adamantyl and 1-norbornyl moieties. Additionally, R⁹, R¹⁰, R¹¹and R¹² can each be an independently selected neutral substituentrepresented by Formula I:

-A-O—[—(CR**₂)_(q)—O—]_(p)—(CR″₂)_(q)—OH  Formula I

[0040] where A and q are as defined before, but R** is selected from ahalogen.

[0041] Therefore it will be appreciated that polymers in accordance withembodiments of the present invention encompass repeat units derived frompolycyclic olefin monomers in accordance with any one of Formulae A, Band C. Such monomers can be produced by a variety of methods where suchmethods, as well as catalyst systems for the polymerization of suchmonomers are discussed in detail in U.S. Pat. Nos. 5,468,819, 5,569,730,6,136,499, 6,232,417 and 6,455,650, the disclosures of which areincorporated, in pertinent part, herein. Exemplary methods of formingpolycyclic olefin monomers include, Diels-Alder condensations employingcyclopentadiene and an appropriate dienophile or the reaction of anappropriately substituted polycyclic olefin with a desired exo isomermol %, with a reagent appropriate for forming the final monomer desired.

[0042] As disclosed herein above, it has been found that monomers havinga desired exo isomer mol % affect the dissolution rate of polymers madetherefrom advantageously. In some embodiments, this desired exo isomermol % is greater than the exo isomer mol % that would be expected for apolycyclic olefin monomer based on the thermodynamic equilibrium of theisomers of the monomer obtained from a Diels-Aider reaction. In otherembodiments, the desired exo isomer mol % is less than the exo isomermol % that would be expected for a polycyclic olefin monomer based onthe thermodynamic equilibrium of the isomers of the monomer obtainedfrom a Diels-Alder reaction. Such desired exo isomer mol % monomers canbe obtained by selecting appropriate portions of monomer duringpurification using, for example, fractional distillation methods.However, obtaining such monomers is not limited to fractionaldistillation or any other purification method. Rather, such desired exoisomer mol % monomers useful for embodiments of the current inventioncan be obtained by any appropriate method and these appropriate methodsand the monomers obtained therefrom are within the scope and spirit ofthe present invention.

[0043] It should be understood that the polymers in accordance withembodiments of the present invention encompass at least one polycyclicolefin repeat unit derived from a polycyclic olefin monomer having adesired exo isomer mol %. However such polymers can also encompassrepeat units derived from a variety of other types of monomers. Forexample, such polymers can include repeat units derived from maleicanhydride monomers, acrylate monomers, trifluoromethylacylate monomersand the like, as well as mixtures of such various types of monomers. Inaddition, polymers in accordance with the present invention can beformed using any appropriate polymerization method including vinyladdition, ring opening metathesis polymerization (ROMP) and free radicalmethods with the proviso that the polymerization method does notsignificant alter the exo isomer mol % of the polycyclic olefin monomeremployed. It should also be understood that polymers in accordance withthe present invention are not limited to having a single repeat unithaving a desirable exo isomer mol %. Thus, polymers encompassing two ormore such repeat units are also within the scope and spirit of thepresent invention.

[0044] Advantageous polymers produced in accordance with the presentinvention encompass addition polymerized polycyclic repeat units linkedvia 2,3-enchainment. Such polymers include at least one monomerencompassed by Formula C, as defined above, and optionally one or moremonomers encompassed by Formulae A and/or B and of any of the othermonomer types mentioned above. At least one of such monomers has adesired exo isomer mole % such that the resulting polymer will have adesired dissolution rate or imaging property. Advantageously, thedesired exo isomer mol % of the at least one monomer can be obtained by,for example, selecting an appropriate cut or fraction from a fractionaldistillation of the monomer. However other methods for obtaining amonomer with the desired exo isomer mol % can also be employed, forexample by preparing the monomer in a manner that results directly inthe desired exo isomer mol %.

[0045] It will of course be realized that the resulting dissolution rateand/or imaging property of a polymer employing a repeat unit having thedesired exo isomer mol % is also dependent on the relative amount ofsuch repeat unit incorporated within the polymer. Thus, where a polymerincorporates a relatively low concentration of the repeat unit havingthe desired exo isomer mol %, such low repeat unit concentration cancorrelate to little or no effect on the dissolution rate or imagingproperty of the polymer. However where the concentration of the desiredexo isomer mol % repeat unit is high, a significant effect on thedissolution rate or imaging property of the resulting polymer isobserved. For example, referring to Table 2, below, it is seen that forthe polymers of Examples 24, 25 and 26 (about 87% HFANB), thedissolution rate of the polymer behaves in essentially the same manneras is observed for the HFANB homopolymers of Examples 1-23. Wherehowever, the amount of HFANB is reduced, such as in blends of HFANBhomopolymer with other materials such as the P(TBTFMA-VENBHFA) copolymerdiscussed below, the observed effect can be reduced.

[0046] Embodiments of the present invention can also include polymersformed from more than one polycyclic olefin monomer having a reactivependant group (where “reactive” refers to a protected acid labilependant group or a pendant group involved in the dissolution of theresulting polymer). Thus for each of these monomers there can be adifferent desired exo isomer mol %. While the combination of suchdifferent monomers into a single polymer can require someexperimentation to determine the appropriate exo isomer mol % for eachmonomer and the relative concentration of each monomer within thepolymer, Applicants believe that such experimentation is straightforward and well within the ability of one having ordinary skill.

[0047] It should be realized by now, that embodiments in accordance withthe present invention include both the polymers formed by vinyl additionpolymerization, as well as the cyclic olefin monomers employed forforming such polymers, where at least one of such cyclic olefin monomershas a desired exo isomer mol %. In addition, it will be understood thatthe polymers of some embodiments in accordance with the presentinvention encompass at least one monomer selected from those inaccordance with each of Formulae A, B and C. Such polymers, as well asothers in accordance with the present invention, are useful for formingphotoresist compositions having a desired dissolution rate and imagingproperty. Some embodiments in accordance with the present invention willencompass positive tone (positive acting) polymers and the photoresistcompositions made therefrom. Other embodiments will encompass negativetone (negative acting) polymers and the photoresist compositions madetherefrom. It should be appreciated that the specific monomers having adesired exo isomer mol % that are selected, will include pendant groupsthat are appropriate for the type of photoresist composition (positiveor negative) desired. It should also be apparent that where someembodiments of the present invention will encompass monomers and theresulting repeat units having an enhanced exo isomer mol %, otherembodiments of the present invention will encompass monomers and theresulting repeat units having an enhanced endo isomer mol %. It shouldalso be noted that the pendant groups of monomers, and the resultingrepeat units, in accordance with the present invention may or may not beprotected with acid labile groups. Finally, embodiments in accordancewith the present invention include the selection of monomers having adesired exo isomer mol % for combination with any of the variousadditives used in formulating photoresist compositions. For example,such additives can include photoacid generators, photoinitiators,dissolution rate modifiers and the like, where any of such additives canbe monomeric, oligomeric or polymeric in nature.

[0048] The various aspects of the invention will be appreciated morefully in light of the following illustrative examples and exemplaryformulas for polymers in accordance with the present invention. Suchexamples are for illustrative purposes only and are not to be construedas limiting the scope and spirit of the present invention. Unlessspecifically noted otherwise, the molecular weight of the resultingpolymers prepared in the following examples, where reported, wasdetermined using GPC methods in THF with a poly(styrene) standard.

Synthesis Example 1

[0049] α,α-bis(trifluoromethyl)bicyclo[2.2.1]hept-5-ene-2-ethanol((HFANB) 80.0 g, 0.292 mol, endo/exo ratio was 44/56),N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate ((DANFABA)0.0468 g, 0.0584 mMol) and sufficient toluene to bring the total volumeto 200 mL were added to a glass pressure reactor. The mixture was purgedwith hydrogen gas for 30 min then charged with hydrogen (90 psig). Thereaction mixture was heated to 80° C. The pressure was relieved and thepalladium catalyst, palladium bis(di-isopropylphenylphosphine) diacetate(0.0071 g, 0.012 mMol) was added. The reactor was immediatelyrepressurized with hydrogen gas (90 psig) and allowed to react for 18 h.The reaction mixture was cooled and then filtered through a 0.22 micronTeflon® filter to remove black palladium metal. The resulting filtratewas added to heptane to precipitate the polymer as a white powder. Thepowder was collected by filtration and dried in a vacuum oven at 90° C.Yield 52.5 g (66%). Mw=11,300; Mn=5440.

Synthesis Example 2

[0050] HFANB (19.2 g, 0.701 mol, endo/exo ratio was 70/30), DANFABA(0.0112 g, 0.0140 mMol) and sufficient toluene to bring the total volumeto 47 mL were added to a glass pressure reactor. The reactor was chargedwith 17 psig ethylene and then heated to 80° C. The pressure wasrelieved and the palladium catalyst, palladiumbis(di-isopropylphenylphosphine) diacetate (3 mL of a 0.93 mMol solutionin methylene chloride) was added. The reactor was immediatelyrepressurized with ethylene (17 psig) and allowed to react for 20 h. Thereaction mixture was cooled and added to an excess of hexane in order toprecipitate the polymer. The polymer was collected by filtration anddried in a vacuum oven at 80° C. Yield 9.5 g (50%).

[0051] The polymer was then dissolved in 48 mL of toluene. To thismixture was added 24 mL of glacial acetic acid, 12 mL of hydrogenperoxide (30%), and 12 mL of water. The mixture was heated to 80° C. for3 h. The organic layer was separated and washed four times with water.The organic layer was then concentrated by rotary evaporation thenpoured into heptane to precipitate the polymer. The polymer wascollected by filtration and dried in a vacuum oven at 80° C. Yield 8.8g. The polymer was redissolved in methanol and precipitated by additionto water. Mw=6400; Mn=3630.

Synthesis Example 3

[0052] Synthesis Example 2 was repeated except that a pressure of 5 psigethylene was used. Yield 11.4 g (59%). The polymer was treated withglacial acetic acid and hydrogen peroxide as in Synthesis example 2.Yield 10.5 g. Mw=12900; Mn=5930.

Synthesis Example 4, 5 and 6

[0053] Synthesis examples 4, 5, and 6 were made in a manner identical toSynthesis example 3, but different levels of ethylene were used toaccess different molecular weights. Yields are found in Table 1, below.The polymers were treated with glacial acetic acid and hydrogen peroxideas in Synthesis example 3. The polymer's molecular weights are found inTable 1, below.

Synthesis Example 7

[0054] HFANB (19.2 g, 0.701 mol, endo/exo ratio was 70/30), DANFABA(0.0112 g, 0.0140 mMol) and sufficient toluene to bring the total volumeto 47 mL were added to a glass pressure reactor. The mixture was chargedwith hydrogen gas (90 psig). The reaction mixture was heated to 80° C.The pressure was relieved and the palladium catalyst, palladiumbis(di-isopropylphenylphosphine) diacetate (3 mL of a 0.93 mMol solutionin methylene chloride) was added. The reactor was immediatelyrepressurized with hydrogen (90 psig) and allowed to react for 18 h. Thereaction mixture was cooled and then filtered through a 0.22 micronTeflon® filter. The resulting filtrate was added to heptane toprecipitate the polymer as a white powder. The powder was collected byfiltration and dried in a vacuum oven at 80° C. Yield 11.6 g (61%).Mw=17,860; Mn=7270.

Synthesis Example 8

[0055] Synthesis Example 7 was repeated except that hydrogen was spargedthrough the reaction mixture for 15 min prior to pressurizing thereactor with 90 psig hydrogen. Yield 9.95 g (52%). Mw=7900; Mn=4150.

Synthesis Example 9

[0056] Synthesis example 1 was repeated except that the endo/exo ratioof the monomer was 85/15. The polymer was isolated by precipitation intohexane.

[0057] Yield 65.1 g (80%). Mw=8870; Mn=4880.

Synthesis Example 10

[0058] Synthesis example 9 was repeated except that the endo/exo ratioof the monomer was 85/15 and the hydrogen pressure was 50 psig. Thepolymer was isolated by precipitation into hexane. Yield 60.6 g (76%).Mw=13600; Mn=5700.

Synthesis Example 11

[0059] Synthesis example 9 was repeated except that the endo/exo ratioof the monomer was 85/15 and the hydrogen pressure was 50 psig. Thepolymer was isolated by precipitation into hexane. Yield 61.9 g (77%).Mw=11600; Mn=5820.

Synthesis Example 12

[0060] HFANB (40.0 g, 0.146 mol, endo/exo ratio was 90/10), DANFABA(0.0351 g, 0.0438 mMol), triethylsilane (2.31 mL, 14.4 mMol), ethanol(0.940 mL, 16.2 mMol), and toluene (68 mL) were added to a glass vial.The bottle was capped with a septum and mixture was sparged withnitrogen for 15 min. The mixture was then heated to 80° C. and thecatalyst, [palladiumbis(triisopropylphosphine)(acetonitrile)(acetate)][tetrakis(pentafluorophenyl)borate] (0.017 g, 0.0146 mMol) was added in a minimum of 1,2-dichloroethane.The mixture was allowed to react for 18 h. The reaction mixture wascooled and added to heptane to precipitate the polymer as a whitepowder. The powder was collected by filtration, washed with heptane anddried in a vacuum oven at 100° C. Yield 30.7 g (77%). The polymer wasredissolved in toluene and reprecipitated into heptane, filtered anddried in a vacuum oven at 100° C. Mw=4670; Mn=3120.

Synthesis Example 13

[0061] Synthesis example 12 was repeated except that only 0.28 mL (0.177mol) of triethylsilane was employed. Yield and molecular weights arereported in Table 1, below.

Synthesis Example 14

[0062] Synthesis example 12 was repeated except that 1.1 mL (0.0069 mol)of triethylsilane was employed. Yield and molecular weights are reportedin Table 1, below.

Synthesis Example 15

[0063] Synthesis example 12 was repeated except that only 0.55 mL(0.0034 mol) of triethylsilane was employed. Yield and molecular weightsare reported in Table 1, below.

Synthesis Example 16

[0064] HFANB (100 g, 0.365 mol, endo/exo ratio was 78/22), DANFABA(0.088g, 0.110 mMol), triethylsilane (5.8 mL, 36 mMol), ethanol (2.3 mL, 40mMol), and toluene (171 mL) were added to a glass vial. The vial wassealed with a septum and heated to 80° C. and the catalyst, [palladiumbis(triisopropylphosphine)(acetonitrile)(acetate)][tetrakis(pentafluorophenyl)borate] (1.0 mL of a 0.0025 M solution in methylene chloride) was added. Themixture was allowed to react for 18 h. The reaction mixture was cooledand a small amount of acetone was added to reduce the viscosity of thesolution. The reaction mixture was added to a ten-fold excess of hexaneto precipitate the polymer as a white powder. The powder was collectedby filtration and dried in a vacuum oven at 90° C. Yield 30.1 g (73%).Mw=5350; Mn=3270.

Synthesis Example 17

[0065] Synthesis example 16 was repeated except that 3.1 mL (19 mMol) oftriethylsilane was employed. Yield and molecular weights are reported inTable 1, below.

Synthesis Example 18

[0066] Synthesis example 16 was repeated except that 1.8 mL (11 mMol) oftriethylsilane was employed. Yield and molecular weights are reported inTable 1, below.

Synthesis Example 19

[0067] Synthesis example 16 was repeated except that 1.2 mL (7.5 mMol)of triethylsilane was employed. Yield and molecular weights are reportedin Table 1, below.

Synthesis Example 20

[0068] Synthesis example 16 was repeated except that 0.89 mL (5.6 mMol)of triethylsilane was employed. Yield and molecular weights are reportedin Table 1, below.

Synthesis Example 21

[0069] HFANB (41.1 g, 0.150 mol, endo/exo ratio was 58/42), DANFABA (1.0mL of a 0.0075 M solution in methylene chloride), triethylsilane (1.73g, 0.0148 mol), ethanol (0.77 g, 0.017 mol) and sufficient toluene tobring the total volume to 100 mL were added to a glass vial. Thereaction mixture was heated to 80° C. The palladium catalyst,bis(di-isopropylphenylphosphine) diacetate was added (1 mL of a 0.0025 Msolution in methylene chloride) to the monomer solution. After 18 h, thereaction mixture was cooled and then added to hexane to precipitate thepolymer as a white powder. The powder was collected by filtration anddried in a vacuum oven at 90° C. Yield 30.2 g (73%). Mw=5770; Mn=3560.

Synthesis Example 22

[0070] Synthesis example 21 was repeated except that 0.54 mL (4.6 mMol)of triethylsilane was employed. Yield and molecular weights are reportedin Table 1, below.

Synthesis Example 23

[0071] Synthesis example 21 was repeated except that 0.27 mL (2.3 mMol)of triethylsilane was employed. Yield and molecular weights are reportedin Table 1, below.

Synthesis Example 24

[0072] HFANB (51.0 g, 0.186 mol, endo/exo ratio was 90:10),5-norbornene-2-hydroxyethylether ((HEENB) 2.36 g, 0.0140 mol),triethylsilane (2.58 g, 0.0222 mol), ethanol (1.02 g, 0.0222 mol) andsufficient toluene to bring the total volume to 133 mL were added to aglass vial. The reaction mixture was heated to 80° C. DANFABA (1.0 mL ofa 0.06 M solution in methylene chloride) and [palladiumbis(triisopropylphosphine)(acetonitrile)(acetate)][tetrakis-(pentafluorophenyl)borate] (1.0 mL of a 0.02 M solution inmethylene chloride) was added. After 18 h, the reaction mixture wascooled and then added to 40 mL of Amberlite GT-73 (Rohm and Haas) andDiaion CRBO2 (Mitsubishi Chemical) resin beads. This slurry was shakenovernight. The resin beads were removed by filtration to give acolorless filtrate. The filtrate was concentrated by rotary evaporationand then added to a 10-fold volumetric excess of hexane to precipitatethe polymer. The polymer was collected by filtration and dried in avacuum oven at 90° C. Yield 24.6 g (46%). Mw=4610; Mn=3260. The molarratio of HFANB:HEENB was found to be 88:12 by ¹³C NMR measurements.

Synthesis Example 25

[0073] Synthesis example 24 was repeated except that the monomer'sendo/exo ratio was 70:30. Yield 19.9 g (37%). Mw=6740; Mn=4580. Themolar ratio of HFANB:HEENB was found to be 86:14 by ¹³C NMRmeasurements.

Synthesis Example 26

[0074] Synthesis example 24 was repeated except that the monomer'sendo/exo ratio was 58:42. Yield 20.9 g (39%). Mw=7140; Mn=4590. Themolar ratio of HFANB:HEENB was found to be 87:13 by ¹³C NMRmeasurements.

[0075] Dissolution Rate Method 1 for Examples 1-23

[0076] A quartz crystal microbalance (QCM) was employed to study thekinetics of dissolution of the polymer films formed from the severalpolymers of Examples 1-23 in an aqueous base developer. The quartzcrystals employed in this study had an inherent frequency of about 5MHz. A Maxtek TPS-550 sensor probe and PI-70 driver were used inconjunction with a Phillips PM6654 programmable high resolutionfrequency counter and an IBM PC. The instrument was controlled and datawere collected by a custom-made LabView software program. The polymerwas dissolved in propylene glycol methyl ether acetate (⅕ wt/wt) and thesolution was filtered down to 0.2 μm. Polymer films were prepared byspin-casting on 1″ quartz discs and baked at 130° C. for 60 sec and thenthe coated discs were mounted on a QCM probe. In 0.26 Ntetramethylammonium hydroxide (TMAH) (CD-26), the dissolution of thepolymer is more or less linear with time, allowing the calculation ofthe rates (A/sec) from the slopes of the thickness-development timeplots.

[0077] The results of these measurements are shown in FIG. 3. Here, thedissolution rate (DR) of each polymer of the aforementioned examples isplotted as a function of a number-average molecular weight (IAn) and exomol % of the HFANB monomer employed for the polymerization. It should benoted that the plot seems to indicate that the DR of the homopolymerdoes not seem to be affected by Mn (or Mw)of such polymer. Rather, wherethe exo concentration of the beginning monomer is high (i.e., 42%) DR isslow (3500-3900 Å/sec), and where the exo concentration of suchbeginning monomer is low (i.e., <25%) the DR is as much as two timesfaster (6000-7300 Å/sec).

[0078] Dissolution Rate Measurements Example 2.

[0079] The copolymers from Synthesis Examples 24, 25, and 26 weredissolved in PGMEA to between 20-25% solids.

[0080] A clean silicon wafer (Silicon Quest, <1,0,0>) was spin coatedwith 1 mL of hexamethyldisilazine (HMDS), 500 rpm for 10 seconds and2000 rpm for 60 seconds, then baked at 130° C. for 90 seconds.Approximately 1 mL of the filtered (0.2 micron) polymer solution wasapplied to the center of the wafer and spun as described above. TheWafer was soft baked at 130° C. for 120 seconds to ensure the removal ofall of the casting solvent.

[0081] Cauchy parameters and film thickness of the samples weredetermined using a J. A. Woollam M2000 ellipsometer.

[0082] Dissolution rate measurement was performed using a reflectometrybased Dissolution Rate Monitor, collected and controlled using a custommade Lab-View system, using single wavelength versus time,interferometry data. The developer was aqueous tetramethyl ammoniumhydroxide (Shipley, TMAH 2.38%). Samples were developed using a puddletechnique in which aliquots of developer are placed upon the film, andfilm thickness was measured vs. time. The slope of the line of athickness vs. time plot yields dissolution rate and was expressed asÅ/second. Results of these measurements are presented in Table 2.

[0083] As in DR data plotted in FIG. 3, and discussed above, thedissolution rates of the polymers of Examples 24, 25, and 26 seem moredependent upon the exo mol % in the starting HFANB monomer. Thusseemingly regardless of molecular weight, the higher the exo mol %, thelower the DR.

[0084] Polymer Blend Formulation And Imaging

[0085] poly(t-butyl2-trifluoromethylacrylate-co-5-[(1,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]norbornan-2-ylvinyl ether) (P(TBTFMA-VENBHFA) copolymer) and an HFANB homopolymer (1/1wt/wt) (one of Examples 12, 15, 16, 19, 21 and 23) were blended bydissolving equal weights of each in propylene glycol methyl etheracetate to make a 10 wt % polymer solution. Di-t-butylphenylidodoniumperfluorooctanesulfonate (4%) and tetrabutylammonium hydroxide (0.15%)were added to the polymer solution. The solution was filtered (0.2 μm).The solution was then spin-cast and the resulting films baked at 130° C.for 60 sec, exposed to 193 nm radiation through a binary chrome-on-glassmask, post exposure-baked at 130° C. for 90 sec, and then developed witha commercially available 0.26 N tetramethylammonium hydroxide solution.

[0086] Referring to FIGS. 4 and 5, scanning electron micrographs of spincast films, such as described above, are shown after exposure (120nanometer (nm) lines and spaces) and image development. In FIG. 4, themicrographs are of the relatively high Mn blends that use thehomopolymers of Examples 23, 19 and 16. As seen, the image quality isbest for the polymer blend having the highest exo mol %. In FIG. 5; themicrographs are of the relatively low Mn blends that use thehomopolymers of Examples 21, 16 and 12. As seen, the image quality seemsrelatively uniform for all samples with no obvious trend in imagequality visible and/or corresponding to exo mol %. However it is mostinteresting to note that the best imaging result of FIG. 4 is comparableto the imaging results of FIG. 5 despite the significant difference inmolecular weight of the HFANB homopolymer employed in the blend. Thisresult is unexpected and suggests that control of exo isomer mol % canprovide a relatively uniform imaging quality of a broad range ofmolecular weights. Thus providing a wider processing window both for theactual imaging and for the composition of the photoresist.

[0087] The copolymer is represented by the structure below where thepercentages are the relative concentration of the individual monomers inthe copolymer.

[0088] Thus, it can be said from the imaging results presented above,that when the molecular weight of HFANB homopolymer is high (see, FIG.4), the best image quality is seen where the exo mol % of the HFANBstarting polymer is the highest (58/42). Where the exo mol % is low(90/10), the image is severely bridged.

[0089] Where the molecular weight of the HFANB starting monomer is low(FIG. 5), it seems as if the performance of all the blends is uniformlygood and independent of exo mol %. Thus, by providing a desired exoisomer mole percent in at least one repeating unit of a polymer used ina photoresist composition, control of the differential dissolution rateappears to allow for a broad range of polymer molecular weights toprovide good image quality. TABLE 1 Endo: DR Ex. No. Yield Mw Mn CTA*Peracid Exo (Å/sec) 1 66% 11300 5440 H₂ No 44/56 4089 2 50% 6400 3630C₂H₄ Yes 70/30 3916 3 60% 12900 5930 C₂H₄ Yes 70/30 2741 4 60% 163008000 C₂H₄ Yes 70/30 3552 5 62% 28000 12100 C₂H₄ Yes 70/30 3361 6 60%36200 15500 C₂H₄ Yes 70/30 3516 7 61% 17860 7270 H₂ No 70/30 2904 8 52%7900 4150 H₂ No 70/30 3428 9 80% 8870 4880 H₂ No 85/15 6432 10 76% 136005700 H₂ No 85/15 5801 11 77% 11600 5820 H₂ No 85/15 6570 12 77% 46703120 Et₃SiH No 90/10 6588 13 72% 31230 14380 Et₃SiH No 90/10 6486 14 76%8980 5260 Et₃SiH No 90/10 7300 15 65% 16510 8530 Et₃SiH No 90/10 6526 1677% 5350 3270 Et₃SiH No 78/22 6627 17 87% 9030 5070 Et₃SiH No 78/22 604518 89% 15700 7490 Et₃SiH No 78/22 6740 19 91% 22700 10600 Et₃SiH No78/22 6423 20 93% 31900 13700 Et₃SiH No 78/22 6543 21 73% 5770 3560Et₃SiH No 58/42 3920 22 91% 16400 7520 Et₃SiH No 58/42 3850 23 77% 2870012900 Et₃SiH No 58/42 3510

[0090] TABLE 2 Endo: Example # Yield Mw Mn CTA Exo DR (Å/sec) 24 46%4610 3260 Et₃SiH 90/10 1920 25 37% 6740 4580 Et₃SiH 70/30 510 26 60%7140 4590 Et₃SiH 48/52 460

We claim:
 1. A photoresist composition comprising a polymer comprisingat least one polycyclic olefin derived type of repeat unit having adesired exo mole percent.
 2. A method of improving the imagingcapability of a photoresist composition, comprising providing apolymeric resin comprising polycyclic olefin derived repeat units havinga desired exo mole percent.
 3. A method of controlling the differentialdissolution rate of a photoresist composition comprising providing apolymeric resin to the photoresist composition comprising polycyclicolefin derived repeat units having a desired exo mole percent.